There are variety of processes in which a plasma is generated to deposit and/or to remove material. Examples are the process of sputtering, where material is removed from a target and deposited on a substrate in order to produce e.g. a thin film, or the process of etching, where atoms are removed in order to create e.g. a very clean surface.
To produce the plasma, a high voltage is generated between electrodes by means of a suitable power supply device. However, the processing conditions may be such that there is a sudden electrical discharge for instance between the electrodes which causes the occurrence of one or more arcs. Normally, such arc events are to be prevented since they may lead e.g. to damages in the target or to a poor quality of the surface to be processed.
It is widely known to use a switch for interrupting the power supply to the electrodes when an arc event occurs (see e.g. U.S. Pat. Nos. 5,192,894 or 6,621,674 B1). However, interruption of the power supply gives rise to the problem that the energy which is stored e.g. in the cables at the time of interruption is supplied to the plasma, which may impede a quick quenching of the arc. Eventually, the duration until the plasma processing is in an arc-free condition and operates normally may be prolonged.
The patent application US 2004/124077 A1 refers to a power supply which is suitable in the field of so-called HiPIMS (“High Power Impulse Magnetron Sputtering”). The power supply, which produces very short pulses of extremely high power, is provided with a capacitor that is repetitively charged and then discharged through an inductor. When an arc is detected, the capacitor is first disconnected from the inductor by actuating a first switch and then connected to the inductor again by actuating two other switches such that the energy contained in the inductor is recycled to the capacitor. Compared to this recycled energy, the energy contained in any cables connecting the output terminals of the power supply with the plasma processing chamber is negligible. Thus, no measures are provided to recover this energy in the cables.
In the patent application US 2008/309402 A1, it is proposed to use a pre-charging/discharging cicuit for pre-charging a capacitor under normal operating conditions. When an arc is detected, an amount of the residual energy which is stored in the cables leading to the plasma processing chamber is transferred into the capacitor and finally eliminated by means of the pre-charging/discharging circuit before the power is applied again to the plasma processing chamber. Thus, the energy is finally lost, which makes the operation inefficient.
Apart from the problem of the energy in the cables, another problem impeding an efficient handling of arcs may arise when the time of interruption of the power supply is not optimal, e.g. the time is too short to quench an arc.
In the patent U.S. Pat. No. 6,621,674 B1, it is proposed to adjust the time interval during which the voltage is applied to the electrodes in an adaptive manner, whereas the time interval during which the voltage is disconnected is kept constant.